The average woman's body parts are smaller than the average man's because, as described by News Medical, the testosterone boost most men experience during puberty greatly increases their muscle and bone mass. The testosterone-fueled effects of puberty directly lead to an increase in height, adds the You & Your Hormones website.
Testosterone and estrogen both contribute to the growth spurts children experience, states Harvard Health Publications. However, most men start puberty later and are consequently taller when their pubertal growth spurt begins. Furthermore, testosterone increases not just height but also overall bone mass. After a few years, testosterone has the paradoxical effect of closing the growth plates of the long bones, preventing further growth.
The website Transitioning FTM in Australia, in describing the effects of hormonal therapy on transgender males, states that testosterone cannot increase height in adults but it can increase muscle and bone mass, thus increasing the size of limbs and feet. Ligaments also increase in size to keep up with added stress of larger, heavier bones and muscles. The site states that testosterone therapy at a young age can be used to increase adult height but only if the growth plates of the long bones are still open.
News Medical adds that during puberty, testosterone also increases the size of the rib cage. This also contributes to the average gender difference in body size.